This invention relates to electrostatic treatment used for freezing, and freshness keeping of food and oxidation inhibition of edible oil.
Conventionaly, meat and fish were thawed in the range of minus temperature in a refrigerator. Further, fruit as well as meat and fish was kept fresh therein, and these technics are disclosed in Japanese Patent Publication Hei5-77387. In this method, the whole part of a refrigerator is completely insulated from its floor and a voltage of 5,000V to 20,000V is impressed on the shelves of the refrigerator by a negative electron generating apparatus through the inner wall of the refrigerator to thaw food in a low temperature range of xe2x88x923xc2x0 C. to +3xc2x0 C. Further, in the negative electron generating apparatus, one pole of the secondary side of a transformer is completely closed and insulated, and a high output resistance is provided on the other pole.
In these method and apparatus, since one pole of the electron generating apparatus is insulated, a large output is required on the secondary side of the transformer. Further, since the whole part of the refrigerator is insulated from the floor, and the casing of the refrigerator is not grounded, the casing of the refrigerator is charged with electricity, and an operator sometimes receives an electric shock to cause a danger of a secondary accident. In addition, there was a conventional fryer in which oil in an oil tank is charged with electricity to prevent oxidation of the oil. Such a fryer is disclosed in Japanese Patent Publication Hei7-78298, that is, an electrode is set in the oil tank with a high voltage electrostatic transformer or a voltage is directly impressed on the oil tank itself thereby. In this case, the whole part of the fryer is insulated from the floor, one pole on the secondary high voltage side of the high voltage electrostatic transformer is insulated and the other pole is connected to an electrode or the oil tank. However, unless the transformer having one pole thereof insulated and closed is adjusted so that a large output is generated on the secondary side thereof, a necessary voltage cannot be impressed on the oil itself. Further, since the whole of the fryer is insulated from the floor, the casing of the fryer is charged with electricity to cause an electric shock of an operator.
Therefore, it is an object of this invention to provide an electrostatic treatment method and apparatus which are safe and effective even if the secondary side output voltage of the transformer is relatively small.